<?php
interface Store_Interface{
    /**
     * Store value
     * @param string $key
     * @param mixed $val
     * @return void
     */
    function set($key,$val);
    /**
     * Get stored value by key
     * @param string $key
     * @return mixed
     */
    function get($key);
    /**
     * Check if key exists
     * @param string $key
     * @return boolean
     */
    function keyExists($key);
    /**
     * Remove data from storage
     * @param sting $key
     * @return void
     */ 
    function remove($key);
    /**
     * Add value to the storage
     * @param string $key
     * @param mixed $val
     * @return void
     */
    function add($key , $val);
}